Download divided textures in parallel if option is set
Download divided textures in parallel if option is set

- If the parallel cube option is set load divided textures in parallel
- goes a bit faster with the network calls happening at the same time
instead of in sequence. Actual actual creation of texture still happens
one at a time on the main thread I believe.

obsoleted/PyriteDemoClient,PyriteServer/PyriteDemoClient,obsoleted/CubeExplorer,obsoleted/CubeExplorer